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Biology

Genes, inheritance and selection

Extinction

Extinction

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Investigating specimens using microscopes

Investigating the effect of pH on amylase activity

Investigating molecules in food using food tests

Investigating osmosis in potatoes

Investigating the effect of antimicrobials

Investigating limiting factors of photosynthesis

Investigating the rate of respiration

Using field-work techniques

Ecosystems and material cycles

Ecosystems, competition and environmental changes

Trophic levels and biomass transfer

Human impacts on biodiversity

Conservation and maintaining biodiversity

The carbon cycle

The water cycle

Obtaining potable water

The nitrogen cycle

Pollution indicators - Higher

Decomposition and biogas

Exchange and transport in animals

Specialised exchange surfaces

Factors affecting the rate of diffusion

Human circulatory system

Aerobic and anaerobic respiration

Animal coordination, control and homeostasis

The human endocrine system

Hormones: adrenaline and thyroxine - Higher

Hormones in human reproduction

Treating infertility - Higher

Homeostasis and blood glucose

Controlling body temperature

The urinary system

Plant structures and their functions

Photosynthesis and limiting factors

Factors limiting the rate of photosynthesis - Higher

Water and mineral transport in plants

Plant adaptations

Plant hormones

Health, disease and the development of medicines

The relationship between health and disease

Communicable disease

Sexually transmitted infections

How the body fights disease

Vaccination, immunisation and medicines

Aseptic techniques

Drug development and testing

Monoclonal antibodies and their uses - Higher

Non-communicable diseases

Calculating BMI and the waist-to-hip ratio

Cardiovascular disease and treatment

Plant defences and diseases

Natural selection and genetic modification

Evolution by natural selection

Fossils as evidence for evolution

Classifying living organisms

Selective breeding

Uses and evaluation of genetic engineering

The process of genetic engineering - Higher

Uses of genetic engineering

Genetics

Meiosis, sexual and asexual reproduction

Sexual and asexual reproduction

DNA: structure, genes and chromosomes

Protein synthesis - Higher

Inheritance and genetic diagrams

Inherited disorders

Blood groups, co-dominance and haemophilia

Types and sources of variation

The human genome project

Cells and control

The cell cycle and stages of mitosis

Cell differentiation, stem cells and ethics

The structure of the brain

The nervous system and the reflex arc

The eye: structure, reflexes and defects

Key concepts

Eukaryotic and prokaryotic cells

Specialised animal and plant cells

Types of microscopes and calculations

Enzymes

Calorimetry and energy calculations

Transport systems in cells

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Measuring techniques

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Designing experiments

Methods of heating substances

Working with electronics

Random sampling and sampling methods

Comparing results using percentage change

Working scientifically

The scientific method

Science communication and ethics

Evaluating risks and hazards

Collecting data

Processing and presenting data

Units and equations

Structuring a scientific report and drawing conclusions

Uncertainties and evaluations

Explainer Video

Tutor: Holly

Summary

Extinction

In a nutshell

The environment is constantly changing and a species will either adapt to these changes or go extinct. A species is considered extinct when there are no remaining individuals of that species still living. This may be due to the environment changing too quickly, a new predator killing a species, a new disease, or a catastrophic event such as a volcanic eruption. 



Mass extinctions

Mass extinctions occur when the environment changes in a way that means organisms can't compete or reproduce. The fossil record shows five mass extinctions over geological time. 

​

Example

Around 66 million years66\ million\ years66 million years​ ago, it is believed that a huge asteroid killed three quarters of life on Earth, including dinosaurs. The asteroid created a dust cloud that blocked the sunlight. Plants died first due to the lack of light which prevented them photosynthesising. Herbivores became extinct next and then carnivores as they relied on herbivores for their food source. Volcanic eruptions and sea level change also contributed to the extinction.



Invasive and alien species

Another cause of extinction is the introduction of a new species. The new species may be a predator of the existing species or they may compete with the existing species for food. If they are better competitors, the existing species may become extinct. 


The new species could also introduce new diseases that the existing species does not have immunity against. This can cause extinction. 


Example

One reason the Dodo went extinct was because of invasive species. 


Example

Harlequin ladybirds are a new ladybird species in Britain. They eat other ladybirds and outcompete them for food. There is a risk that the native ladybirds may become extinct. 



Sixth mass extinction

Some scientists believe that humans are currently causing a sixth mass extinction by polluting the Earth, changing the landscape and exploiting species. 


Example

Bees pollinate over 70%70\%70%​ of the crop species that provide 90%90\%90%​ of the global food supply. If bees go extinct, scientists worry that humans may become extinct soon after.


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Learn with Basics

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Adapting to different environments

Unit 1

Adapting to different environments

Extinction and species preservation

Unit 2

Extinction and species preservation

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Extinction

Unit 3

Extinction

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FAQs - Frequently Asked Questions

Could there be a sixth mass extinction?

Some scientists believe that humans are currently causing a sixth mass extinction by polluting the Earth, changing the landscape and exploiting species.

How do invasive species cause extinction?

Invasive species can cause extinction as the new species may be a predator of the existing species or they may compete with the existing species for food.

What are mass extinctions?

Mass extinctions occur when the environment changes in a way that means organisms can't compete or reproduce.

How do species become extinct?

The environment is constantly changing and a species will either adapt to these changes or go extinct.

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